STEROID-SENSITIVE NEURONES IN RAT BRAIN - ANATOMICAL LOCALIZATION AND RESPONSES TO NEUROHUMOURS AND ACTH

The effects of dexamethasone-phosphate, microelectrophoretically delivered, on single unit activity in the brain of intact rat under combined urethane-chloralose anaesthesia was studied. Dexamethasone-phosphate-sensitive cells were accurately identified histologically and localized in the hypothalamus and in the midbrain scattered over wide areas. Of these neurones the large majority were clearly inhibited and a small number activated. No steroid-sensitive neurones were found in the cortex, the dorsal hippocampus or in the thalamus. The steroid-sensitive neurones were also responsive to microelectrophoretically applied acetylcholine and noradrenaline. Acetylcholine predominantly activated these cells, whereas with noradrenaline inhibition rather than activation was observed. Locally delivered ACTH activated the steroid-sensitive neurones. These results may suggest that specific nerve cells in the hypothalamus and midbrain are sensitive to both hormonal and humoural factors and involved in negative and positive feedback actions of the hormones. © 1969.